Lithium manganese oxide spinel compounds such as Li.sub.1+X Mn.sub.2-X O.sub.4+Y have been used as positive electrode material for 4 V secondary lithium and lithium-ion batteries. Typically, these spinel compounds are formed by firing (calcining) a mixture of a manganese source compound and a lithium source compound.
Exemplary manganese source compounds include manganese carbonate (MnCO.sub.3), electrochemical manganese dioxide (.gamma.-MnO.sub.2 or EMD), and chemical manganese dioxide (.gamma.-MnO.sub.2 or CMD).
As described in coassigned U.S. Pat. No. 5,789,115, the mean particle size and particle size distribution of these compounds and, in particular, Li.sub.1+X Mn.sub.2-X O.sub.4+Y, is dependent on the mean particle size and particle size distribution of the raw materials used to make these compounds and specifically the manganese source compound. In addition to affecting the particle size and particle size distribution of the lithium manganese oxide, the morphology, e.g., density and porosity, of the manganese source compound can affect the morphology of the resulting lithium manganese oxides. In particular, the crystal growth of the spinel phase using a low density manganese compound causes an increase in the distance between the spinel crystallites and has a negative effect on the final density of the spinel compound. This presents a problem with MnCO.sub.3 and CMD because these manganese source compounds have relatively low densities and thus produce a low density product. Because EMD has a higher density than MnCO.sub.3 and CMD, EMD is often used instead of these manganese source compounds to produce spinel compounds. Nevertheless, the combined water, porosity and vacancies in the EMD structure have a negative effect on the density of the resulting spinel compound.
The morphology of the manganese source compound also affects the tap and pellet density of the spinel compound. The tap and pellet density are important properties characterizing positive electrode materials for secondary lithium and lithium-ion batteries. In particular, these properties directly influence the specific cell energy, cell safety performance, manganese dissolution, capacity fade and capacity loss at room and elevated temperatures, for the electrochemical cell. Therefore, providing a method for preparing lithium manganese oxide spinel compounds having a desired tap and pellet density is of great importance in developing high energy density and high electrochemical performance 4 V secondary lithium and lithium ion batteries.